1. Technical Field
The present invention relates generally to air conditioning systems and more particularly to an air conditioning system which utilizes a refrigeration system having two evaporators.
2. Discussion
Most modern automotive vehicles have air conditioning devices which both cool and dehumidify the air drawn into and circulated within the passenger compartment of the vehicle. These air conditioning devices typically employ a single evaporator to chill the air being circulated through the air conditioning system. This approach, however, has several inherent drawbacks.
One significant drawback concerns the efficiency of the evaporator at different humidity levels. The evaporators having relatively high heat transfer rates tend to flood at higher humidity levels, causing a build-up of condensate on the heat transfer surface which substantially reduces the efficiency of the evaporator. To combat such situations, many air conditioning systems have relied on hydrophilic coatings or less efficient evaporator designs, including those with fewer fin counts. Hydrophilic coatings increase the surface tension on the heat transfer surface to facilitate a "shedding" effect to drain condensation from the heat transfer surface to prevent the condensate from bridging the fins. Such coatings are relatively expensive to apply and lose their effectiveness over time such that the shedding effect produced does not last the life of the vehicle. As such, the evaporator efficiency is reduced over time even where hydrophilic coatings are employed.
The refrigeration system compressor compensates for any degradation in evaporator performance which results from the loss in effectiveness of hydrophilic coatings by working the refrigeration system compressor harder (e.g., more frequently and/or longer). The compressor typically consumes a large amount of power when it operates, which results in a substantial penalty in power available for use in propelling the vehicle. This problem is particularly troublesome when such systems are incorporated into automotive vehicles as the fuel economy and performance of the vehicle can be substantially impaired during the operation of the air conditioning system.
Accordingly, there remains a need in the art for an improved refrigeration system for an air conditioning system that provides improved heat transfer efficiency over a predetermined range of humidity levels.